Kin'u is a secondary character in Yashahime: Princess Half-Demon - The Second Act. She is the elder twin daughter of the demon slayer Sango and the monk Miroku, making her the older sister of Hisui, a young demon slayer who works alongside the half-demon princesses. As a child, she and her younger twin sister Gyokuto were seen wearing a green kimono with a dark green fan pattern and a red sash, often barefoot. In her adulthood, she has taken up the vocation of a Buddhist nun, dressing in a monk's tunic with a rosary around her neck and straw sandals. Physically, she is identical to her twin sister, with a slender figure, fair skin, brown eyes, and short dark brown hair.

Kin'u possesses a cheerful and energetic personality that contrasts with the more calm and reserved demeanor of her twin, Gyokuto. She tends not to take things very seriously and is prone to making jokes and light of situations, displaying a confident attitude, particularly regarding her own spiritual powers. Her upbringing as the child of two experienced fighters has shaped her sense of duty. She appears to be close with her family and is enthusiastic about family matters, having been shown to be excited at the news of a new birth and eager to give the baby plenty of attention.

Kin'u's role in the story is that of a supporting character, often appearing alongside her family to lend aid in battles against demons. She and Gyokuto, along with their mother Sango, are shown fighting to defend the village from demonic threats. Her training as a nun means her primary contribution to such fights is her spiritual power, which she uses in a supportive capacity. For example, her growing spiritual abilities helped Sango forge and strengthen the Black Hiraikotsu, a powerful boomerang weapon capable of purifying and pacifying multiple demons or evil spirits at once. In one instance, she and Gyokuto arrived to assist their brother Hisui in a fight against the octopus demon Takonyudo, which had captured Princess Aiya. During this encounter, Kin'u and Gyokuto quickly noticed that Princess Aiya had developed a crush on Hisui and playfully encouraged their brother in response.

In terms of her family relationships, she is part of the close-knit unit comprising her parents, her twin, and her younger brother. She maintains a connection to Kaede, the elderly village priestess, having accompanied her on walks and assisted her with information about demon sightings in the area. Kin'u's notable abilities stem from her training as a Buddhist nun. She wields spiritual power known as reiryoku, which falls within the category of Buddhist or holy powers. This spiritual energy can be used for various effects, including purification, which makes her effective against demons and evil spirits. Her power is significant enough to be channeled into weapons like the Black Hiraikotsu, enhancing their demon-destroying capabilities. This development of her spiritual abilities continues throughout the series, marking her growth as a nun. Her character does not undergo significant dramatic change, but she consistently serves as a capable and reliable member of the next generation of warriors and spiritualists.